By Barnaby King 05/06/2017

The transition to an energy independent Exeter

Exeter to be Energy Independent and Congestion Free by 2025

That’s the objective, but is this feasible? How could it happen? These are big questions, but vitally important ones. Two reports have been released which provide insight to this (1) provides a detailed discussion of the potential of different technologies to contribute to an energy independent exeter. Whilst also considering the issues and barriers to its realisation. (2) outlines the energy strategy of Exeter city council who aspire to become 100% renewable energy, and energy neutral by 2022. There is a key difference between these two terms; energy independence and energy neutrality. Energy independence describes a system which is totally independent of any other supply, generating all the energy it needs when it needs. Energy neutrality simple requires a system to generate the same amount of energy as it uses over a period of time. The intermittency of renewable energy means energy neutrality would put a large strain on the grid, exporting a lot of energy to the grid at times of excess generation and having a large energy deficit at time of high demand.

To make the transition from energy neutrality to energy independence, storage is required. Acting like a big sponge, it’s able to store and provide energy on demand.  But how much storage would be required to make Exeter energy independent? We built an energy model of Exeter on matlab to investigate this.

The predicted annual demand of exeter at 2030 is 11 TWh (1)

The model took values from (1) for the consumption of Exeter.

  • 40% commercial
  • 17% industrial
  • 43% domestic

The energy mix used:

Controllable generation

  • 25%   GWh CHP
  • 17%   GWh biomass
  • 8%    GWh energy from waste

Intermittent generation

  • 23%   GWh solar
  • 27%   GWh wind
  • 0.1%  GWh hydro

It was assumed that the capacity of the controllable generation, was such as to meet its given percentage of the peak demand.  

 The results shown in table 1 show that 7 GWh of storage would be required to make exeter 100% energy independent. This is a considerable amount of storage. It is equivalent to dinorwig power station,the largest energy storage system in the UK. it’s also equivalent to 7000 1MWh battery which would fill a 75m by 75m cube.  

In reality this storage is an unfeasible amount. There are two reasons for this:

  1. Making  a small area energy independent using storage is not very efficient. Over a larger area, the intermittency of renewable energy and demand are both reduced as things become averaged over a larger area. Therefore less storage is required to balance this out.
  1. While energy storage will always be required to match urgent demand. Behavioural change of the end user also has a massive part to play. It’s estimated that as much as 40%  (3) of all demand could be flexible. By combining smart storage systems with controllable demand, energy independence would become much more feasible.

Energy independence

(%)

100

98

95

92

Storage               

(GWh)

7

5

4

2.5

Power capacity  

(GW)

0.6

0.45

0.45

0.4

To conclude while exeter becoming more energy independent is a noble goal, a large amount of behavioural change and consumer participation is required to support energy storage in balancing the system. How to encourage und users to take part is the topic of much research and innovation. QBOTs believe that by combining storage with a smart energy management system able to manage the flexible demand of the building, asset owners will be able to maximise their profits, allowing for maximum adoption of both technologies.

(1)   https://www.cityscience.com/download/Energy-Independence-2025.pdf

(2)   http://committees.exeter.gov.uk/documents/s56069/Energy%20Strategy%202017-2022.pdf .

(3)   http://www.sciencedirect.com/science/article/pii/S0306261914011623